JEE Main 2023 · 31 January · evening · Single correct · +4 / −1
Considering a group of positive charges, which of the following statements is correct ?
- (a) Net potential of the system cannot be zero at a point but net electric field can be zero at that point
- (b) Net potential of the system at a point can be zero but net electric field can't be zero at that point.
- (c) Both the net potential and the net electric field cannot be zero at a point.
- (d) Both the net potential and the net field can be zero at a point.
Answer and solution
Answer (a) Net potential of the system cannot be zero at a point but net electric field…
Solution
Physics sir · 3 steps
Potential adds as plain positive numbers, but field adds as arrows, so only the arrows can cancel.
- Potential is a scalar. Each positive charge gives V = kq/r at a point, and with q > 0 and r > 0 every term is positive. A sum of positive numbers can never be zero, so the net potential (zero taken at infinity) is never zero at any finite point.
Vₙₑₜ = k(q₁/r₁ + q₂/r₂ + …) > 0
- Field is a vector. Each charge pushes its field away from itself, so fields from different charges can point in opposite directions. At the midpoint of two equal positive charges the two fields are equal in size and opposite in direction, so the net field there is zero.
- So. The potential cannot be zero but the field can be, which is option (a).
The idea to keep. With charges of one sign only, V never vanishes at a finite point because scalars cannot cancel. E⃗ can vanish wherever the vectors balance, such as between like charges.
Answer from the NTA final answer key. Solution by PrepWiser.